private Texture2D SpriteTexture;
private Vector2 origin;
private Vector2 screenpos;
protected override void LoadContent()
{
    // Create a new SpriteBatch, which can be used to draw textures.
    spriteBatch = new SpriteBatch(GraphicsDevice);
    SpriteTexture = Content.Load<Texture2D>("ship");
    Viewport viewport = graphics.GraphicsDevice.Viewport;
    origin.X = SpriteTexture.Width / 2;
    origin.Y = SpriteTexture.Height / 2;
    screenpos.X = viewport.Width / 2;
    screenpos.Y = viewport.Height / 2;
}

private float RotationAngle;
protected override void Update(GameTime gameTime)
{
    // Allows the game to exit
    if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
        this.Exit();

    // The time since Update was called last.
    float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;

    // TODO: Add your game logic here.
    RotationAngle += elapsed;
    float circle = MathHelper.Pi * 2;
    RotationAngle = RotationAngle % circle;

    base.Update(gameTime);
}

protected override void Draw(GameTime gameTime)
{
    graphics.GraphicsDevice.Clear(Color.CornflowerBlue);

    // TODO: Add your drawing code here
    spriteBatch.Begin();
    spriteBatch.Draw(SpriteTexture, screenpos, null, Color.White, RotationAngle,
        origin, 1.0f, SpriteEffects.None, 0f);
    spriteBatch.End();

    base.Draw(gameTime);
}